As for "gimmick" versus "idea", yes, honestly that makes a lot more sense, it ties in with the whole "details make the story YOURS" idea. Anyone can make up an angel of death, but how you handle the plot points, etc, that's what makes the story truly yours and yours alone. An idea conjures up a vague image, like "I don't want anyone doing an angel of death story until I do it!" which, obviously, is impossible as I think the whole angel of death trope is as old as time. Hell, I've got one! But saying you have an idea you feel sets yours apart, or as you put it, a "gimmick", it makes much more sense.
